This invention relates to a method for controlling a clutch. In particular, the invention relates to a method for controlling a clutch for an engine-powered system, such as an air conditioner system, to minimize a vehicle vibration due to a torque pulse generated by actuation of the clutch.
Air conditioner systems have long been utilized in automotive vehicles to enhance the comfort of vehicle occupants. Referring to FIG. 1, an automotive vehicle 10 is illustrated. Referring to FIG. 2, the vehicle 10 may include a conventional air conditioner system 11 that circulates a cooling medium. The air conditioner system 11 includes a compressor 12, a condenser 14, an expansion valve 16, an evaporator 18, and a pressure sensor 20. Referring to FIG. 1, the compressor 12 is mounted on an automotive engine 22 and is powered by the engine 22 via a driven belt 40, a pulley 36 and a clutch 24. The clutch 24 has a first state torsionally engaged with the compressor 12 and a second state disengaged from the compressor 12. When the clutch 24 is torsionally engaged with the compressor 12, the compressor 12 is driven by the belt 40. The compressor 12 compresses the cooling medium and delivers the cooling medium to the condenser 14, which transfers heat from the cooling medium. The condenser 14 delivers the cooling medium to the expansion valve 16 that expands the cooling medium into a gaseous form. The expansion valve 16 delivers the cooling medium to the evaporator 18 which transfers heat from air in a vehicle passenger compartment (not shown) to the cooling mediumxe2x80x94to thereby cool the interior of the passenger compartment.
Referring to FIG. 3A, the engine 22 for powering the air conditioner system 11 is illustrated. The engine 22 is resting on engine mounts 28, 30 of the vehicle 10 and has a longitudinally extending torque roll axis 32. Referring to FIGS. 2 and 3A, the engine 22 includes a crankshaft 34, pulleys 36, 38, a belt 40, the clutch 24, and the compressor 12. The remaining components of the engine 22 have been removed for clarity of illustration. Referring to FIGS. 3A and 3B, during operation of the engine 22, the engine 22 rocks back and forth about the torque roll axis 32 at a natural frequency. The rocking motion of the engine 22 is generally called an oscillating roll movement. The natural frequency of the oscillating roll movement will vary with different engines and powertrains, but remains relatively constant at different engine speeds for a given engine and powertrain. FIGS. 3A and 3B illustrate the two extremes of the oscillating roll movement of the engine 22.
Referring to FIG. 3A, during operation of the engine 22, an external reaction torque is applied to the engine 22 by the powertrain (not shown) of the vehicle 10xe2x80x94in response to the torque applied by the engine 22 to the powertrain. As illustrated, the direction of the external reaction torque (counter-clockwise in FIG. 3A) is opposite the direction of the crankshaft rotation (clockwise in FIG. 3A).
The engagement of the clutch 24 to drive the compressor 12 results in an almost instantaneous reduction in the engine torque (not shown) and thus an almost instantaneous reduction in the external reaction torque. This instantaneous reduction in the external reaction torque is effectively a torque pulse in a direction counter to the direction of the external reaction torque (clockwise in FIG. 3A). As a result of the torque pulse, the vehicle occupants may feel an undesirable vibration during the engagement of the clutch 24.
Similarly, the disengagement of the clutch 24 results in an almost instantaneous increase in the engine torque (not shown) and thus an almost instantaneous increase in the external reaction torque. This instantaneous increase in the external reaction torque is effectively a torque pulse in the same direction as the external reaction torque (counter-clockwise in FIG. 3A). Similarly, as a result of the torque pulse, the vehicle occupants may feel an undesirable vibration during the disengagement of the clutch 24.
There is thus a need for a method of controlling a clutch for an engine-powered system in an automotive vehicle that minimizes or reduces one of more of the above-mentioned deficiencies.
The present invention provides a method of controlling a clutch for an engine-powered system (such as an air conditioner system) in an automotive vehicle to reduce and/or minimize a vehicle vibration due to a torque pulse generated by engaging and disengaging the clutch.
Referring to FIG. 3A, it has been determined that the best time in the natural oscillating roll movement of an engine to engage a clutchxe2x80x94and to absorb a corresponding torque pulse (in a clockwise direction in FIG. 3A)xe2x80x94is when the engine is moving at a maximum velocity and therefore momentum in a direction counter to the direction of the torque pulse (in a counter-clockwise direction in FIG. 3A). Thus the optimum time to engage the clutch is at the mid-travel position of the roll (i.e., position of maximum velocity) when the engine is moving in a counter-clockwise direction about the torque roll axis. Since there may be a small delay from the time the clutch is energized to the time the clutch actually engages a compressor, the optimum time to energize the clutch may be slightly before the mid-travel position.
Similarly, it has been determined that the best time in the natural oscillating roll movement of the engine to disengage the clutchxe2x80x94and to absorb a corresponding torque pulse (in a counter-clockwise direction in FIG. 3A)xe2x80x94is when the engine is moving about at a maximum velocity and therefore momentum in a direction counter to the direction of the torque pulse (in the clockwise direction in FIG. 3A). Thus the optimum time to disengage the clutch is at the mid-travel position of the roll (i.e., position of maximum velocity) when the engine is moving in a clockwise direction about the torque roll axis. Since there may be a small delay from the time the clutch is de-energized to the time the clutch actually disengages, the optimum time to de-energize the clutch may be slightly before the mid-travel position.
A method for controlling a clutch for an engine-powered system (such as an air conditioner system) in an automotive vehicle, includes the steps of generating an engine roll signal responsive to an oscillating roll movement of an engine about a torque roll axis. The method further includes the step of determining a direction of the oscillating roll movement utilizing the engine roll signal. Finally, the method includes the step of actuating the clutch responsive to an operational parameter of the engine-powered system and the direction of said oscillating roll movement. The operational parameter may be a pressure measurement in the air conditioner system.
An automotive vehicle in accordance with the present invention includes a clutch having a first state torsionally engaged with a component of an engine-powered system and a second state disengaged from the component of the engine-powered system. The vehicle further includes a first sensor generating a first signal indicative of an operational parameter of the engine-powered system. The vehicle further includes a second sensor generating a second signal responsive to the oscillating roll movement of the engine indicative of a direction of the oscillating roll movement. Finally, the vehicle includes a controller for actuating the clutch responsive to the operational parameter of the engine-powered system and to the direction of the oscillating roll movement. The engine-powered system may comprise an air conditioner system with a compressor driven by the engine.
A method and an automotive vehicle in accordance with the present invention represent a significant improvement over conventional methods and vehicles. In particular, the method and vehicle minimizes the vibration during the engagement and disengagement of a clutch from an air conditioner compressor. As a result, the vehicle occupants have a more comfortable ride in the vehicle when the air conditioner is turned on or off.
These and other features and advantages of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.